Actuator Test Research Articles

A new kind of hydraulic proportional loading method for actuator testing based on the relief valve controlled cylinder

A new kind of hydraulic proportional loading method based on the relief valve-controlled cylinder has been researched. The math model for the loading torque and the rotation angle has been deduced according to the loading principle, which proves their relationship is approximately linear within a certain rotation scale; the direction of the loading torque has also been analysed under different states of change valve. In order to reduce the rotary inertia and improve the dynamic performance, a connecting rod mechanism has also been designed to optimize the connection structure between the cylinder and the swing arm, accompanied with comparative analysis and simulation. Based on theory research, two sets of actual loading devices have been developed, which were certified by the loading experiments of a kind of electro-hydraulic actuator. Research and experiment results have proved that this hydraulic proportional loading method, with a simple control principle and easy engineering constructability, can supply approximately linear loading torque for actuator experiments within a ±90° scale, and the structure optimization by the connecting rod mechanism can eliminated overshoot and oscillation successfully.

Characterization of mixed-mode I/II fracture properties of adhesively bonded yellow-poplar by a dual actuator test frame instrument

Abstract Experimental results for the fracture behavior under mixed-mode in-plane loading conditions of adhesively bonded wood specimens are reported. The material systems considered involved yellow-poplar (Liriodendron tulipifera), a hardwood of the Magnoliaceae family, as adherends bonded with two different adhesives, a moisture-cure polyurethane (PU) and a phenol/resorcinol/formaldehyde (PRF) resin. A dual actuator test frame permitted fine scanning of fracture behavior over a full range of mixed-mode I/II levels for double cantilever beam (DCB) geometry specimens. These tests showed that, in the considered material systems, the critical strain energy release rate, c, tends to increase as the mode-mixity of the loading increases. In particular, the increase is steeper in proximity to pure mode II loading for the PRF bonded specimens. The experimental values of c obtained were fairly scattered, as is common when testing wood systems. This variability is due in part to the natural variability of wood but also to other factors such as the orientation of the grain in the bonded beams and variations of bondline thickness. In particular, measurements of adhesive layer thickness were performed. This analysis was implemented with microscopic examination of samples cut from untested DCB specimens, where the bondline had not been disrupted by the test. Although the wood parts were power planed prior to bonding, rather large variations of the adhesive layer thickness were observed: on the order of 1–100 μm for specimens bonded with the PU resin and 10–50 μm for specimens bonded with the PRF resin, which showed somewhat more consistent fracture behavior.

The Research on Control Type and Control Strategy of Synchronous Hydraulic Closed-loop Control System

Open loop control of hydraulic driven synchronously, because it relies entirely on the hydraulic control the synchronous drive of the actuator to control the accuracy of the components themselves, rather than the output of the actuator testing and feedback, so it can not eliminate or inhibit the adverse effects of high-precision synchronization. In this paper, the hydraulic control system for the classification of synchronization, comparison of the various types of control strategies, applications, and hydraulic synchronous control system for practical application in industry.

스프링-점성형 비틀림 진동댐퍼 설계 및 성능 평가에 관한 연구

Design routines of a torsional spring-viscous damper for a 1800 kW four cycle diesel engine-generator system are described. Modal techniques for system normalization and optimal equations for damper design are used to obtain proper design parameters of the damper. A prototype damper is manufactured according to the described design process and its two design parameters, stiffness and damping, are evaluated experimentally by torsional actuator test and free decay test. Experimentally obtained values of stiffness and damping coefficients showed good agreements with the designed values of the prototype damper.

The Development and Experiment of the MSMA Actuator Test Platform Based on LabVIEW

Data acquisition is very important for control precision of micro-positioning platform. Based on LabVIEW, a kind of MSMA (Magnetically Controlled Shape Memory Alloy) test platform was developed, and the data acquisition, programming and testing was studied. The deformation mechanism of MSMA was analyzed, and the characteristics of MSMA were obtained by experimental study, the relationship curves between displacement and current, and the curves between magnetic field and current were tested. Experiments show that the test platform for intelligent materials is excellent and reliable, and the paper provided a good research platform for the study on properties of intelligent materials.

Numerical analysis of the dual actuator load test applied to fracture characterization of bonded joints

The dual actuator load test was numerically analyzed in order to assess its adequacy for fracture characterization of bonded joints under different mixed-mode loading conditions. This test enables asymmetric loading of double cantilever beam specimens, thus providing a large range of mixed-mode combinations. A new data reduction scheme based on specimen compliance, beam theory and crack equivalent concept was proposed to overcome several difficulties inherent to the test. The method assumes that the dual actuator test can be viewed as a combination of the double cantilever beam and end loaded split tests, which are used for pure modes I and II fracture characterization, respectively. A numerical analysis including a cohesive mixed-mode damage model was performed considering different mixed-mode loading conditions to evaluate the test performance. Some conclusions were drawn about the advantages and drawbacks of the test.

Combining Model-Based and Feature-Driven Diagnosis Approaches – A Case Study on Electromechanical Actuators

Model-based diagnosis typically uses analytical redundancy to compare predictions from a model against observations from the system being diagnosed. However, this approach does not work very well when it is not feasible to create analytic relations describing all the observed data, e.g., for vibration data which is usually sampled at very high rates and requires very detailed finite element models to describe its behavior. In such cases, features (in time and frequency domains) that contain diagnostic information are extracted from the data. Since this is a computationally intensive process, it is not efficient to extract all the features all the time. In this paper we present an approach that combines the analytic model-based and feature-driven diagnosis approaches. The analytic approach is used to reduce the set of possible faults and then features are chosen to best distinguish among the remaining faults. We describe an implementation of this approach on the Flyable Electromechanical Actuator (FLEA) test bed.

Airborne Electro-Mechanical Actuator Test Stand for Development of Prognostic Health Management Systems


 
 
 With the advent of the next generation of aerospace systems equipped with fly-by-wire controls, electromechanical actuators (EMA) are quickly becoming components critical to safety of aerospace vehicles. Being relatively new to the field, however, EMA lack the knowledge base compared to what is accumulated for the more traditional actuator types, especially when it comes to fault detection and prognosis. Scarcity of health monitoring data from fielded systems and prohibitive costs of carrying out real flight tests create the need to build high-fidelity system models and design affordable yet realistic experimental setups. The objective of this work is to build an EMA test stand that, unlike current laboratory stands typically weighing in excess of one metric ton, is portable enough to be easily placed aboard a wide variety of aircraft. This stand, named the FLEA (for Flyable Electromechanical Actuator test stand), allows testing EMA fault detection and prognosis technologies in flight environment, thus substantially increasing their technology readiness level – all without the expense of dedicated flights, as the stand is designed to function as a non-intrusive secondary payload. No aircraft modifications are required and data can be collected during any available flight opportunity: pilot currency flights, ferry flights, or flights dedicated to other experiments. The stand is currently equipped with a prototype version of NASA Ames developed prognostic health management system with models aimed at detecting and tracking several fault types. At this point the team has completed test flights of the stand on US Air Force C-17 aircraft and US Army UH-60 helicopters and more experiments, both laboratory and airborne, are planned for the coming months.
 
 

Electrical and electromechanical properties of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide-blended cellulose

The effect of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMITFSI) blending on the electromechanical and electrical properties of cellulose was premeditated by taking bending actuator test and electrical impedance analysis. Dispersion of BMITFSI in cellulose matrix was carried out by solution blending technique. Upon blending BMITFSI, bending displacement of the actuator was enhanced by eight times as compared to that of the pristine cellulose. Similar improvement in the AC conductivity of cellulose was observed. The effect of BMITFSI content and humidity on electromechanical and electrical properties of BMITFSI-loaded cellulose was discussed.

Fabrication and testing of cellulose EAPap actuators for haptic application

Piezoelectric behavior of the cellulose electro-active paper (EAPap) actuators is studied for a possible haptic actuator. Using a thin stretched EAPap film with a material fiber orientation of 45°, stacked and unimorph EAPap actuators are prepared and their performance is investigated as functions of frequency and applied electric field. A small actuation displacement is observed from the stacked EAPap actuator. The displacement of the stacked actuator is dependent on the actuation frequency. The actuation displacement and resonance frequency of the unimorph type EAPap actuators are investigated with different beam lengths. At 1 Hz, the piezoelectric constant d 33 of the 32-layer-stacked EAPap actuator is about 150 pm/V and decreases as the operating frequency increases. A unimorph EAPap actuator with 60 mm length and 10 mm width shows a 75 μm of bending displacement at 10 Hz. From the experimental study, we demonstrate the feasibility of the cellulose EAPap for haptic applications.

Biaxial experimental determination of in-plane matrix fracture envelope of unidirectional composite

A test procedure for the determination of the in-plane fracture envelope of unidirectional fibre reinforced polymers (FRP) is presented. In particular, the determined fracture envelope covers combined in-plane shear and transverse (perpendicular to the fibre direction) matrix strength. The proposed test procedure allows the manufacture of specimens for material fracture characterisation in the same way that real composite structures are usually produced for the automotive industry. The biaxial testing is performed using a custom-made dual actuator test machine and keeping the ratio of transverse and shear load constant until fracture. The experimentally obtained transverse–shear strength relation can be well represented by the matrix fracture model by Puck. It is shown that the stress concentrations in the gauge section of the flat biaxial specimens can be avoided by the introduction of a thickness reduction, whereas the stress concentrations within biaxial specimens without such a thickness reduction lead to significantly lower strength.

Study on Error Measurement Method for Actuator Frequency Characteristic Test System

System error measurement is key step in actuator frequency characteristic test and practical system error measurement methods must be studied to provide qualified results for system error compensation. Two error measurement methods (swept sine and FFT: fast Fourier transform) are explored, a strong anti-jamming frequency characteristic algorithm is perfected for swept sine and digital smoothing is introduced for improving accuracy of FFT. Numerical examples verified accuracy and robustness of swept sine and validity of FFT. These methods were applied to measure system error in missile actuator test system, the experiments showed that swept sine method could gain smooth and stable results and FFT method could achieve rather close results with swept sine. This study is part of general test system of some missile and provides valid technology analysis and reliable measurement results of system error for its actuator test.

Effect of porosity and pore size on microstructures and mechanical properties of poly‐ε‐caprolactone‐ hydroxyapatite composites

The influence of variant pore-size and porosity on the microstructure and the mechanical properties of poly-epsilon-caprolactone (PCL) and hydroxyapatite (HA) composite were examined for an optimal scaffold in bone tissue engineering. Three various amounts of sodium chloride (NaCl, as porogens) with two distinct particle size ranges (212-355 mum and 355-600 mum) were blended into PCL and HA mixture, followed by a leaching technique to generate PCL-HA scaffolds with various pores and porosity. The porosities of the scaffolds were correlated with the porogen size and concentration. The morphological properties of the resulting scaffolds were assessed by micro-computerized tomography (muCT), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). Extensive PCL-HA pore interconnections with thinner pore walls were present in scaffolds with higher concentration (4:1 w/w) and larger particulate of porogen used in the fabrication process. Embedding of HA particles in the scaffold resulted in rough surfaces on the composites. Instron actuator testing indicated that the tensile strengths and Young's moduli of scaffolds were influenced by both the porosities and pore sizes of the scaffold. It was apparent that increasing the concentration of porogen compromised the mechanical properties; and a larger porogen particle size led to increased tensile strength but a reduction in Young's modulus. Overall, the data indicated that modification of the concentration and particle size of porogen altered the porous features and mechanical strength of HA-PCL scaffolds. This provided means to manipulate the properties of biocompatible cell-supporting scaffolds for use as bone graft substitutes.

Leakage Fault Detection in Hydraulic Actuators Subject to Unknown External Loading

AbstractThis paper describes development and experimental evaluation of a hydraulic actuator leakage fault detector based on the extended Kalman filtering (EKF). Identification of external leakage at either side of the actuator as well as the internal leakage between the two chambers is examined. The present work is built upon previous work by the authors, but incorporates a significant improvement in that the new scheme is capable of detecting leakage faults for actuators that are also subject to unknown loading and/or significant friction. Experiments on a laboratory-based hydraulic actuator, using both structured (sinusoidal) and unstructured (pseudorandom) test signals show that: (i) under normal (no- fault) operating condition, the EKF-based state estimator closely predicts the states of the system and the external load, including actuator friction, using only a few measurements, (ii) in the presence of leakage faults, the level of residual errors between the estimated and the measured line pressures...

Dynamic loading systems for ground testing of high speed aerospace actuators

PurposeTo develop structured guidelines for the synthesis of dynamic force simulators that are required for the testing of high speed aerospace actuators. To provide realistic and proven solutions at both test bench hardware and control design levels.Design/methodology/approachThe state of the art in control design applied to load simulators in mainly based on complex controllers and does not take into account practical considerations. The objective of the present work is to provide generic preliminary design rules to ensure that the test bench architectures (frame, power transmission and control) and the components specifications are consistent with the targeted performance. Once selected the appropriate power transmission architecture, a linear approach is used as a foundation to generate design rules. Then, preliminary design is achieved thanks to the introduction, as early as possible, of the unavoidable technological defects.FindingsA step‐by‐step methodology allows the designer to select the controller architecture and to specify components with special care to their consistency with the required dynamic performance. The linear then practical approach generates key rules that can be used in the very early phase of the test bench design.Originality/valuePractical considerations on the components static and dynamic limitations are introduced progressively to make the natural test bench performance as consistent as possible with the performance requirements. Consequently, the controller becomes simpler to design and robust.

Deep-reactive ion-etched compliant starting zone electrostatic zipping actuators

This paper presents the modeling, design, fabrication and testing of monolithic electrostatic curved-electrode zipping actuators fabricated by deep reactive ion etching (DRIE). In contrast to traditional curved-electrode zipping actuators, the design of the actuators presented here utilizes a compliant starting cantilever to significantly reduce the initial pull-in voltage by closing the gap (kerf) generated by DRIE. Thus, the actuators achieve high actuation force at a relatively low voltage. For example, two actuators each with dimensions of 4.5 mm*100 /spl mu/m*300 /spl mu/m are used to drive a bistable MEMS relay. Together, the two actuators provide up to 10 mN of force over their 80 /spl mu/m stroke at 140 V. Measurements of the force-displacement relation of these actuators confirm theoretical expectations based both on numerical and analytical methods. Finite element analysis is employed to predict the behavior of the complete bistable relay system. [1231].

Investigation into Tangential Force and Axial Stress Effects on Fretting Fatigue Behavior

Fretting fatigue behavior of a titanium alloy was investigated using a dual actuator test setup which was capable to apply the pad displacement independent of the applied cyclic load on specimen. Fretting fatigue tests were conducted using this setup with a phase difference between cyclic load on the specimen and tangential force on the fretting pad with cylinder-on-flat contact configuration under partial slip condition. Two axial stress ratios were used. The relative slip range and tangential force range were related to each other and this relationship was not influenced by phase difference, axial stress ratio, and contact load under the partial slip condition. Change in the phase difference caused the change in relative slip as well as tangential force for a given applied pad displacement and axial load. However, there was no effect of phase difference on fretting fatigue life at a given relative slip level. Fretting fatigue tests with a fully reversed axial stress showed longer fatigue life than tension-tension counterparts at a given relative slip, tangential force range, and axial stress range. Finite element analysis was conducted by including the complete load history effects, which showed that stress distribution on the contact surface stabilized after the first fatigue cycle. Unlike relative slip and∕or tangential force range, a critical plane-based parameter appears to take into account the stress ratio effects to characterize fretting fatigue behavior.

Fretting behavior of shot peened Ti–6Al–4V under slip controlled mode

Fretting tests of shot peened Ti–6Al–4V were conducted under slip controlled mode using a dual actuator test setup which could apply an independent pad displacement at a given applied bulk stress. Fretting regime was identified based on the hysteresis loop of tangential force versus relative slip range and the evolution of tangential force. Fretting regime changed from partial slip to mixed slip and then to gross slip with increasing relative slip range, and the transition from mixed to gross slip occurred at a relative slip range of ∼50 μm regardless of the applied bulk stress magnitude for both shot peened and unpeened specimens. Fretting fatigue life initially decreased as the relative slip range increased and reached to a minimum value, and then increased with an increase of the relative slip range due to the transition in fretting regime from mixed slip to gross slip. Shot peened specimens had longer fatigue life than unpeened specimens at a given relative slip range, but the minimum fatigue life was at the same value of the relative slip range for both shot peened and unpeened specimens. The relationship between relative slip and fatigue life was also found to be independent of the applied bulk stress level. Further, tangential force was directly related to relative slip and this relationship was independent of other fretting variables.

Performance evaluation of lightweight piezo-composite actuators

This paper is concerned with the performance evaluation and comparison for several kinds of lightweight piezo-composite actuator (LIPCA) device system. LIPCA device system is composed of a piezoelectric ceramic wafer layer and fiber reinforced light composite layers, typically a PZT ceramic layer is sandwiched by a top fiber layer with low coefficient of thermal expansion (CTE) and base layers with high CTE. To investigate the effect of lay-up structure of the LIPCA on the actuating performance, five kinds of actuator with different lay-up stacking sequence have been designed, manufactured, and tested. The performance of each actuator was evaluated using an actuator test system consisted of an actuator supporting jig, a high voltage actuating power supplier, and a non-contact laser measuring system. From the comparison of the performance of the LIPCA prototypes, it was found that the actuator with higher coefficient of unimorph actuator can generate larger actuating displacement.

Dry release fabrication and testing of SiC electrostatic cantilever actuators

This paper presents a simple, dry etching-based surface micromachining technique for the fabrication of single-layer polycrystalline 3C–SiC electrostatic actuators. The technique has utilized a single inductively coupled plasma recipe to etch and release metal patterned SiC structural layers. To demonstrate the simplicity of the process, SiC cantilever actuators with different beam lengths have been successfully fabricated using this method. By applying a combination of ac and dc voltages, the fabricated devices have been electrostatically actuated. The fundamental resonance frequencies of fabricated cantilevers with different lengths have been observed to range from 66.65 KHz to 1.729 MHz. The amplitudes of the fundamental resonance peaks with respect to the excitation voltages have also been systematically studied.